This explanatory note provides additional information on Amnesty International’s characterization of the 1988 prison massacres in Iran as “extrajudicial executions” in its December 2018 report Blood-soaked secrets: Why Iran’s 1988 prison massacres are ongoing crimes against humanity. The note briefly discusses the terms “summary executions” and “extrajudicial executions” and their application to the 1988 prison massacres. It further addresses the criminal justice implications of the characterization of the 1988 prison massacres as “extrajudicial executions”, including for judicial officials in Iran who were involved in the 1988 prison massacres.